Login

Join for Free!
122503 members
Advertisement
Advertisement

table of contents table of contents

Home » Biology Articles » Neurobiology » Neurobiology of Diseases & Aging » Actions of Caffeine in the Brain with Special Reference to Factors That Contribute to Its Widespread Use » Figures

Figures
- Actions of Caffeine in the Brain with Special Reference to Factors That Contribute to Its Widespread Use

..................................................

Fig. 1.   Effect of caffeine on different biochemical targets in relation to its levels in humans. Note that caffeine is able to significantly block adenosine effects on A2A (most potent) and A1 receptors already at the low concentrations achieved after a single cup of coffee. To inhibit cyclic nucleotide breakdown via inhibition of phosphodiesterase, 20 times higher concentrations are required; to block GABAA receptors, 40 times higher concentrations; and to mobilize intracellular calcium depots, concentrations of 100 times higher are needed. These latter levels are unlikely to be reached in humans by any form of normal use of caffeine-containing beverages (modified from Fredholm, 1980).

figure 1

..................................................

Fig. 2.   The similarity in the distribution of adenosine A2A, dopamine D2, and dopamine D1 receptors in rats. These film autoradiograms (negatives) show the distribution of mRNA (in situ hybridization) or protein (receptor autoradiography with antagonist radioligand) for the three types of receptors in coronal sections of rat brain. Note the excellent colocalization.

figure 2

..................................................

Fig. 3.   A2A receptor mRNA is specifically associated with D2, but not with D1 receptors, with enkephalin, but not with Substance P, and is essentially absent from large aspiny cholinergic neurons. In situ hybridization experiments were carried out using two separate probes in each experiment. A radioactive probe for the adenosine A2A receptor was combined with a nonradioactive probe for preproenkephalin, preprotachykinin, dopamine D1 and D2 receptors, or choline acetyl transferase. Using an image analysis system, the number of cells expressing mRNA for the A2A receptor was calculated as a percentage of the total number of cells expressing mRNA for the other probes. Cells were counted in several areas of the brain, including dorsolateral and dorsomedial caudate putamen (CP), nucleus accumbens (NC) core and shell, and in the olfactory tubercle. Data are from Svenningsson et al. (1997b).

figure 3

..................................................

Fig. 4.   Schematic illustration of the effect of caffeine on striatopallidal and striatonigral neurons. A, potential interactions between A2A and D2 receptors in the GABAergic neurons that comprise the so-called indirect pathway and project to the ventral pallidum. B, a simplified wiring diagram of the nucleus accumbens and some of its input and output structures. Synapses are shown as stimulatory () or inhibitory (open circle). In this part of the figure are also indicated areas where adenosine and dopamine receptor subtypes are enriched. C, the interactions between A1, D1, and glutamate receptors in neurons that comprise the so-called direct pathway. In particular, it should be noted that activation of dopamine D1 receptors can enhance the actions mediated via NMDA receptors. This causes release of adenosine, which activates A1 receptors located on the terminals of the excitatory input. Hereby the release of glutamate is reduced.

figure 4

..................................................

Fig. 5.   The effect of low doses of caffeine, of SCH 58261, and of DPCPX on NGFI-A expression in striatum and cortex. Left, the effect of increasing doses of caffeine (7.5, 15, or 30 mg/kg i.p.) on locomotion and rearing. Middle, the effect of caffeine on the expression of NGFI-A (measured in arbitrary optical density units; O.D.) in the same animals in the dorsal caudate putamen (upper panel-A), ventral caudate putamen (upper middle panel-B), nucleus accumbens (lower middle panel-C), and in several areas of cortex (lower panel-D). Right, the NGFI-A expression (in optical density units; O.D.) in the animals given the adenosine A2A antagonist SCH 58261 or the A1 antagonist DPCPX in the same brain regions. *p 79:753-764].

figure 5

..................................................

Fig. 6.   Biphasic effects of caffeine on rodent behavior. For further details, see text.

figure 6

..................................................

Fig. 7.   Caffeine place conditioning in rats (Patkina and Zvartau, unpublished data). Left, scores of place conditioning (time spent in drug-paired side) across doses of caffeine (mg/kg, i.p.). Rats were allowed to freely investigate a shuttle box. Rats that spent approximately equal amounts of time in the two compartments were, in a second phase, injected with caffeine while in one of the compartments on four consecutive days. To evaluate the preference, the animals were then allowed, in a drug-free state, to freely investigate the shuttle box. Right, score of place conditioning (percentage of animals with place preference/aversion) across doses of caffeine.

figure 7

..................................................

 


rating: 3.93 from 71 votes | updated on: 17 Nov 2006 | views: 152020 |

Rate article:







excellent!bad…